JPH082927A - Bismuth-rare earth element-iron garnet precursor composition and its production - Google Patents

Abstract

PURPOSE:To enable the sufficient crystallization and the suppressed crystal growth at a relatively low baking temperature in the production of a bismuth- rare earth element-iron garnet fine crystal particle by using a precursor composition containing a stoichiometrically excessive bismuth salt. CONSTITUTION:A precursor giving a bismuth-rare earth element-iron garnet expressed by formula [R is Y, La, Ce, Pr, Nd, etc.; M is Al, Ga, Cr, Mn, Sc, In, Ru, Rh, Co, Fe (II), Cu, etc.; 0<x<=3; 0<=y<=5] is produced by adding a basic substance to an aqueous solution containing k<1>$(3-x)mol of an R- containing salt, k<2>Xzmol of a Bi-containing salt [x<z<=(x+2)], k<3>X-(5-y)mol of an Fe-containing salt and k<4>Xy mol of an M-containing salt (k<1>, k<2>, k<3> and k<4> are each independently a coefficient of 0.95-1.05), alkalifying the mixture to precipitate the R-containing salt, Bi-containing salt, Fe-containing salt and M-containing salt as respective hydroxides and separating the precipitates from the aqueous solution.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent magneto-optical characteristics,
The present invention relates to a bismuth rare earth iron garnet precursor for producing bismuth rare earth iron garnet as a magnetic ferrite material suitable for applications such as optical isolators, optical circulators, optical switch optical waveguides, magneto-optical disk media, and displays.

[0002]

2. Description of the Related Art Conventionally, iron garnet material has been known as a magnetic material having a better magneto-optical characteristic than an amorphous alloy material of a rare earth metal and a transition metal. As a magneto-optical magnetic material using such an iron garnet material, a material using an iron garnet material as a polycrystal on a substrate as a vapor-deposited thin film has been proposed (Japanese Patent Publication No. 56-151).
No. 25). The magnetic material using this polycrystalline vapor-deposited thin film has excellent corrosion resistance, and since it is possible to utilize the transmitted photomagneto-optical effect (Faraday effect) of the magnetic film, high sensitivity is obtained. It has the advantage that it has a large Verde constant. However, since it is polycrystalline, it has a drawback that noise increases due to light scattering, birefringence, or domain wall motion at grain boundaries. Further, when the magnetic film is formed on the substrate, it is necessary to heat at least 600 to 700 ° C. or higher, and therefore, there is a problem that only a substrate having heat resistance can be used. In addition, since an expensive vacuum vapor deposition apparatus is required for vapor deposition, the manufacturing cost is high.

On the other hand, the iron garnet material is not used as a polycrystalline vapor-deposited thin film, but is used as a coating thin film by applying a magnetic material coating composition in which iron garnet material particles are dispersed in a resin binder onto a plastic sheet substrate. It is known. When the iron garnet material is used as a coating thin film as described above, a base material using an inexpensive material can be freely used without being limited by the heat resistance of the base material, and an expensive material such as a vacuum vapor deposition device can be used. There is an advantage that it does not require equipment and can be manufactured at low cost by using general coating technology.

As a material using such an iron garnet material as a coating thin film, a coating type magneto-optical recording material using yttrium iron garnet particles has been proposed (Japanese Patent Laid-Open No. 62-119758). However,
The yttrium iron garnet particles have a particle size of 1.
It is as large as 5 μm, and therefore is greatly affected by the scattering of light, so that it is not suitable for the use of light of submicron wavelength.

Therefore, various methods for producing fine iron garnet-based powder have been proposed (JP-A-3-159).
No. 915-159920, No. 4-74722, No. 4-97914, No. 4-97915, No. 4-208501, No. 3-270105, No. 3-270106, No. 4 -23304). The methods proposed in these publications are
Basically, an iron garnet-based material is prepared by adding a base such as sodium hydroxide to an aqueous solution containing the constituent metal ions in almost the same ratio as the formula unit (fu) of the constituent metal elements of the iron garnet-based material. A metal hydroxide mixture (iron garnet-based precursor) in the same proportion as the formula unit of the constituent metal elements of (1) is precipitated, and the precursor is fired at a temperature of 500 ° C. or higher to produce iron garnet-based microcrystalline fine particles. That is. The method for producing iron garnet-based microcrystalline fine particles using such a precursor can be collectively processed, requires a small amount of input energy, is easy to maintain in a firing apparatus, and has a simple synthetic reaction. Therefore, it is very suitable as an industrial manufacturing method.

[0006]

However, when firing the iron garnet-based precursor, in order to bring the magnetic characteristics (saturation magnetic susceptibility) of the iron garnet-based material to a desired value, 5
It is necessary to fire at a temperature of 00 ° C. or higher, but as the firing temperature rises, crystal growth occurs due to a solid-phase reaction, and the obtained powder has a large particle size of several μm to 20 μm and an uneven particle size distribution. There's a problem.

For this reason, it is conceivable to calcine the iron garnet-based precursor at a relatively low temperature in order to keep the particle size of the powder small, but crystallization into iron garnet-based microcrystals becomes insufficient, which is desirable. There is a problem that it is not possible to obtain a sufficient amount of iron garnet-based fine powder having the above characteristics.

As described above, the iron garnet-based precursor is fired while simultaneously satisfying the contradictory requirements of sufficient crystallization and suppression of grain size growth to produce iron garnet-based microcrystalline fine particles having excellent magnetic properties. That has never been possible.

The present invention is intended to solve the above-mentioned problems of the prior art, and is relatively low as an iron garnet precursor for producing iron garnet microcrystalline fine particles having excellent magnetic properties by firing. It is an object to simultaneously satisfy the contradictory requirements of sufficient crystallization by temperature firing and suppression of grain size growth.

[0010]

Means for Solving the Problems When the present inventors produce bismuth rare earth iron garnet-based microcrystalline fine particles as iron garnet-based microcrystalline fine particles, the stoichiometry is used in a precursor composition for producing the bismuth rare-earth iron garnet-based microcrystalline fine particles. It was found that the above object can be achieved by containing an excessive amount of bismuth salt, and the present invention has been completed.

That is, the present invention is based on the formula (1)

[0012]

[Formula 3] _{R 3-x Bi x Fe 5} -y M y O 12 (1) ( wherein, R Y, La, Ce, Pr, Nd, Pm, S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, and one or more elements selected from the group consisting of Lu, M is Al, Ga, Cr, Mn, Sc, In, R
u, Rh, Co, Fe (II), Cu, Ni, Zn, L
i, Si, Ge, Zr, Ti, Hf, Sn, Pb, M
represents one or more elements selected from the group consisting of o, V and Nb, and R and Bi are c in the garnet crystal structure.
Occupies the sites, Fe and M occupy the a and / or d sites in the garnet crystal structure, and O occupies the h sites in the garnet crystal structure. x and y are 0 respectively
It is a number that satisfies <x ≦ 3 and 0 ≦ y ≦ 5. In the bismuth rare earth iron garnet precursor composition for producing a bismuth rare earth iron garnet represented by), k ¹ , k ² , k ³ and k ⁴ are independently 0.95 to 0.95.
When the coefficient is 1.05, the R-containing salt k ¹ · (3-
x) mol, the Bi-containing salt is k ² · z mol, the Fe-containing salt is k ³ · (5-y) mol, and the M-containing salt is k ⁴ · y mol, and z is x. Provided is a bismuth rare earth iron garnet precursor composition, which is a number satisfying <z ≦ (x + 2). Further, the present invention is a method for producing the above-mentioned bismuth rare earth iron garnet precursor composition, wherein k ¹ , k ² , k ³ and k ⁴ are independently adjusted to 0.
When the coefficient is 95 to 1.05, the R-containing salt k ¹ ·
The Bi-containing salt is added to the (3-x) mole by k ² · z mole, F
The e-containing salt is k ³ · (5-y) mol and the M-containing salt is k ⁴ ·.
Aqueous solution containing y mole ratio (where x and y are numbers satisfying 0 <x ≦ 3 and 0 ≦ y ≦ 5, respectively, and z
Is a number satisfying x <z ≦ (x + 2)), and the aqueous solution is made alkaline to make R-containing salt, Bi-containing salt, Fe-containing salt and M-containing salt as hydroxides. There is provided a production method comprising a step of precipitating and separating the precipitate from an aqueous solution.

The present invention will be described in detail below.

The bismuth rare earth iron garnet precursor composition of the present invention used for producing the bismuth rare earth iron garnet of the formula (1) contains R-containing salt, Fe-containing salt, M-containing salt and Bi-containing salt. To do. In this case, each of the bases is not particularly limited, and examples thereof include a hydroxyl group, a carbonic acid group, a nitric acid group, a sulfuric acid group, and the like, but those forming a fine salt are preferable. For example, as a base for obtaining each salt as a fine precipitate in an aqueous system, a base that makes each salt difficult or insoluble is preferable, and a hydroxyl group is particularly preferable.

Regarding the respective content ratios of the R-containing salt, the Fe-containing salt, the M-containing salt and the Bi-containing salt, the R-containing salt and the F-containing salt are
The e-containing salt and the M-containing salt are mixed so that the molar ratio is basically equal to the atomic ratio among R, Fe and M in the bismuth rare earth iron garnet of the formula (1).
In this case, even if there is a dispersion of about ± 5%, the characteristics of the microcrystalline fine particles after firing are hardly affected. Therefore, k ¹ , k ³ and k ⁴ are independently 0.95 to 1.0
When the coefficient is 5, the ratio of the Fe-containing salt is k ³ · (5-y) moles and the M-containing salt is k ⁴ · y moles with respect to the R-containing salt k ¹ · (3-x) moles. To formulate.

The compounding amount of the Bi-containing salt is stoichiometrically R
It should be blended in a ratio of x moles relative to the content salt k ¹ (3-x) moles, but in the present invention, an excess amount of Bi-containing salt is blended in excess of the stoichiometric amount. In this case, B
If the amount of excess i is too large, the saturation magnetic susceptibility of the bismuth rare earth iron garnet microcrystalline fine particles will be reduced, so that the amount is practically set to (x + 2) mol. When the excess of Bi is small, the effect of the present invention cannot be sufficiently obtained. Therefore, it is preferable to increase the stoichiometric amount by 10% or more. With respect to bismuth, even if there is a variation in the composition of about ± 5%, the characteristics of the microcrystalline fine particles after firing are hardly affected. Therefore, k ² is 0.95
When the coefficient is 1.05 and the compounding amount of Bi is z, z is a number that satisfies x <z ≦ (x + 2).

When the molar precursor composition containing an excessive amount of Bi-containing salt is baked as described above, the temperature required for the solid phase reaction can be lowered as the amount of Bi is increased, It is possible to lower the firing temperature required for crystallization of iron garnet. Therefore, a solid phase reaction occurs at a relatively low firing temperature and sufficient crystallization can be achieved. Therefore, it is possible to suppress the growth of crystal grains, which is caused by crystallization at a relatively high firing temperature, and to produce bismuth rare earth iron garnet microcrystalline fine particles of uniform and fine size (submicron unit). it can. Here, the excess Bi-containing salt becomes an oxide after firing, and serves as a dispersion medium for the bismuth rare earth iron garnet microcrystalline fine particles.

When one of the elements selected as R and M in the formula (1) is a stable element having a divalent or monovalent valence, the other is tetravalent or pentavalent. It is preferable that the garnet crystal is formed in the state of having an average charge of 3 as the element (1).

Next, a method for producing the bismuth rare earth iron garnet precursor composition of the present invention will be described.

First, with respect to the R-containing salt k ^1. (3-x) mol, the Bi-containing salt is k ² · z mol and the Fe-containing salt is k ³ ·.
An aqueous solution containing (5-y) moles and an M-containing salt in a ratio of k ⁴ · y mole (where x, y, z, k ¹ , k ² , k ³ and k ⁴ are as defined above). ) Is prepared. In this case, it is preferable to use a water-soluble salt for each of them, for example, it is preferable to use a nitrate, a sulfate or a chloride. Further, an organic solvent such as alcohols and ethers can be appropriately added to the aqueous solution, if necessary. Further, the concentration of the metal ion in the aqueous solution is too high, the viscosity of the slurry at the time of the precipitate formation described below becomes too large and uniform reaction becomes difficult, and if it is too low, the production amount of the garnet precursor is reduced and the production efficiency is low. Since it tends to decrease too much, the total of all metal ions is preferably 0.1 to 2.0 mol / l, preferably 0.5 to 1.0 mol / l.

Next, a basic substance is added to this aqueous solution to make it alkaline having a pH of 9 or more, preferably 9.8 or more. As a result, R-containing salt, Bi-containing salt, Fe-containing salt and M-containing salt are precipitated as hydroxides. in this case,
As the basic substance, hydroxides of alkali metals such as sodium and potassium and ammonia water can be used.

The resulting precipitate is separated from the solution by a conventional method, washed sufficiently with water to remove the free base, and then dried to obtain the bismuth rare earth iron garnet precursor composition of the present invention.

Next, a method for producing a magnetic ferrite powder containing mainly bismuth rare earth iron garnet represented by the formula (1) using this bismuth rare earth iron garnet precursor composition will be described.

In producing the magnetic ferrite powder, the average particle size is 5 × 10 ⁻⁸ m to 3 × 10.
Is preferred that the a ^-7 m, more preferably from ^{1 × 10 -7 m~2 × 10 -7} m. This is because when the average particle size is smaller than 5 × 10 ⁻⁸ m, the superparamagnetic property is mainly due to thermal agitation, the ferromagnetic property is lost, and sufficient crystallization becomes difficult. Also,
This is because when the average particle diameter is larger than 3 × 10 ⁻⁷ m, light scattering occurs and noise is generated, which is not preferable. The particle shape of the magnetic ferrite powder is preferably an optically symmetrical shape, particularly a spherical shape. However, if the average particle diameter is sufficiently small and controlled, the optical influence is small, and therefore, a polyhedral shape or a plate shape may be used.

In obtaining the magnetic ferrite powder, the temperature required for crystallizing the bismuth rare earth iron garnet precursor composition of the present invention by firing is too high, the crystallization is not sufficient and the temperature is high. If it is too large, the particles become large and the whole is integrated by firing, so it is preferably 400 to 700 ° C., although it varies depending on the composition of the bismuth rare earth iron garnet fine particle precursor.

The firing time is not particularly limited, but usually 1
It is about 0 minutes to 1 hour. This completes the crystallization by the solid phase reaction. The firing atmosphere is not particularly limited as long as it is an oxidizing condition, but an air atmosphere is generally preferable.
Thus, the magnetic ferrite powder mainly containing the bismuth rare earth iron garnet microcrystalline fine particles of the present invention is obtained.

The magnetic ferrite powder of the present invention can be used as a material for a magnetic material coating composition, and an optical isolator, which utilizes the magnetic material coating composition containing the magnetic ferrite powder of the present invention, Optical circulators, optical switches, optical waveguides, optical memories, display devices, sensors and the like can be preferably manufactured.

[0028]

The bismuth rare earth iron garnet precursor composition of the present invention contains excess Bi as compared to the stoichiometric garnet composition. Therefore, it becomes possible to lower the temperature required for the solid-phase reaction when the magnetic ferrite powder containing bismuth rare earth iron garnet microcrystalline fine particles as a main component is produced by the firing treatment of this precursor composition. Along with this, the growth of crystal grains caused by crystallization at a high temperature is suppressed, and a fine magnetic ferrite powder having a uniform size can be obtained.

[0029]

EXAMPLES The present invention will be described in detail below with reference to examples.

[0030] The compositions shown in Examples 1-3 and Comparative Example 1 Table 1 iron nitrate _{[Fe (NO 3) 3 ·} 9H
₂ O] (manufactured by Kanto Kagaku), yttrium nitrate [Y (N
_{O 3) 3 · 6H 2 O} ] ( manufactured by Kanto Chemical Co., Inc.), bismuth nitrate _{[Bi (NO 3) 3 ·} 5H 2 O] ( manufactured by Kanto Chemical Co., Inc.) a mixed aqueous solution was prepared, pH 1 with nitric acid (manufactured by Kanto Chemical Co., Inc.). It was set to 0 and the whole was set to 1 liter.

[0031]

[Table 1] The temperature of the obtained mixed aqueous solution was adjusted to 25 ° C., and ammonia water (manufactured by Kanto Kagaku Co., Ltd.) was added with stirring to generate a hydroxide precipitate of each metal at pH 10.0. The suspension of the precipitate was filtered and separated into a brown slurry-like precipitate and a filtrate. In addition, about 300 of this brown slurry precipitate
It was mixed with ml of water, washed, and filtered again. The above water washing treatment was repeated 5 times. The obtained precipitate was dried in an oven adjusted to 80 ° C. for 24 hours to obtain a powder of bismuth rare earth iron garnet precursor composition. The composition of the obtained powder sample was analyzed by ICP emission spectroscopy (ICPS-
1000II, manufactured by Shimadzu Corporation). The results are shown in Table 2. In addition, Fe (fu), Y (fu) and B in the table
The numerical value of i (fu) is the formula unit (formul
a unit (fu)) and the corresponding molar ratio,
The value of Bi (fu) is the molar ratio of excess Bi.

[0032]

Table 2 Precursor composition composition (molar ratio) Fe (fu) Y (fu) Bi (fu) + Bi (fu) Example 1 5.1 1.9 1.0 0.5 Example 2 4.9 2.1 1.0 1.0 Example 3 5.0 2.0 1.0 1.0 1.5 Comparative Example 1 5.0 2.0 1.0 1.0 0.0 Each precursor composition powder obtained next. Was roughly pulverized in a mortar, and each sample powder was fired in an electric furnace set at various temperatures of 400 to 900 ° C. for 10 minutes to 4 hours to obtain a magnetic ferrite powder.

In addition, in order to confirm that the firing treatment was sufficiently performed, a part of the powder fired for 4 hours was further fired for 4 hours under the same conditions, and it was confirmed that the saturation magnetization did not change. did.

The obtained magnetic ferrite powder was subjected to X-ray diffraction analysis with respect to firing temperature, saturation magnetization analysis with respect to firing temperature, and transmission electron micrograph photography as shown below.

First, among the magnetic ferrite powders obtained in this way, the magnetic ferrite powders obtained in Examples 1, 3 and Comparative Example 1 were subjected to X with respect to the firing temperature.
Line diffraction analysis was performed. The results are shown in Figure 1.
It shows in (a), FIG.1 (b), and FIG.1 (c). From these figures, it can be seen that magnetic fine powder having a garnet structure is produced in each composition. That is, it is understood that magnetic fine powder having a garnet structure is produced even if a stoichiometrically excessive amount of bismuth is present.

FIG. 2 shows the relationship between the saturation magnetization of these magnetic ferrite powders and the firing temperature. It can be seen from FIG. 2 that magnetic fine powder having a garnet structure was obtained. Furthermore, it can be seen from FIG. 2 that the higher the amount of excess bismuth, the lower the firing temperature required for the crystallization solid-phase reaction. Further, it is shown that the inclusion of excess bismuth tends to reduce the saturation magnetization of the magnetic ferrite powder as a whole.

Further, the magnetic ferrite powders of Examples 1 and 3 and Comparative Example 1 were photographed with a transmission electron microscope to examine the relationship between the firing temperature and the shape and size of the particles. A graphical representation of the results is shown in FIGS. As is clear from these figures, it is understood that as the crystallization solid-phase reaction temperature rises, crystals grow and the grain size increases.

Further, from FIGS. 2 and 5, when the precursor composition having the stoichiometric composition (Comparative Example 1) is subjected to the crystallization reaction in the solid phase, in order to sufficiently crystallize it and increase the saturation magnetization, It turns out that it is necessary to fire at a high temperature. However, it is understood that the particles grow when fired at a high temperature and the particle size becomes larger than necessary.

[0039]

EFFECTS OF THE INVENTION By firing the bismuth rare earth iron garnet precursor composition of the present invention at a relatively low temperature, it is possible to produce iron garnet type microcrystalline fine particles having excellent magnetic properties and a uniform particle size.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction chart of a magnetic ferrite powder according to the present invention.

FIG. 2 is a relationship diagram between the firing temperature and the saturation magnetization of the magnetic ferrite powder according to the present invention.

FIG. 3 is an explanatory diagram showing the relationship between the firing temperature and the particle shape of the magnetic ferrite powder according to the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the firing temperature and the particle shape of the magnetic ferrite powder according to the present invention.

FIG. 5 is an explanatory diagram showing a relationship between a firing temperature and a particle shape of a magnetic ferrite powder according to a comparative example.

Claims (8)

[Claims] [Claim 1] (1) [Equation 1] in _{R 3-x Bi x Fe 5} -y M y O 12 (1) ( wherein, R is Y, La, Ce, Pr, Nd, Pm, S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, and one or more elements selected from the group consisting of Lu, M is Al, Ga, Cr, Mn, Sc, In, R
u, Rh, Co, Fe (II), Cu, Ni, Zn, L
i, Si, Ge, Zr, Ti, Hf, Sn, Pb, M
represents one or more elements selected from the group consisting of o, V and Nb, and R and Bi are c in the garnet crystal structure.
Occupies the sites, Fe and M occupy the a and / or d sites in the garnet crystal structure, and O occupies the h sites in the garnet crystal structure. x and y are 0 respectively
It is a number that satisfies <x ≦ 3 and 0 ≦ y ≦ 5. In the bismuth rare earth iron garnet precursor composition for producing a bismuth rare earth iron garnet represented by), k ¹ , k ² , k ³ and k ⁴ are independently 0.95 to 0.95.
When the coefficient is 1.05, the R-containing salt k ¹ · (3-
x) mol, the Bi-containing salt is k ² · z mol, the Fe-containing salt is k ³ · (5-y) mol, and the M-containing salt is k ⁴ · y mol, and z is x. A bismuth rare earth iron garnet precursor composition having a number satisfying <z ≦ (x + 2). 2. The bismuth rare earth iron garnet precursor composition according to claim 1, wherein z is a number satisfying (1.1x) <z ≦ (x + 2). 3. The R-containing salt, Bi-containing salt, Fe-containing salt or M-containing salt wherein the base is a hydroxyl group.
Bismuth rare earth iron garnet precursor composition according to. 4. The method according to claim 1, wherein x is 3 and Y is 0.
The bismuth rare earth iron garnet precursor composition according to any one of 3 above. 5. The method for producing a bismuth rare earth iron garnet precursor composition according to claim 1, wherein k ¹ , k ² and k
^{When 3} and k ⁴ are independently set to a coefficient of 0.95 to 1.05, the R-containing salt is k ¹ · (3-x) mol, the Bi-containing salt is k ² · z mol, and the Fe-containing salt is In an amount of k ³ · (5-y) mol and an M-containing salt in a ratio of k ⁴ · y (where x and y are 0 <x ≦ 3 and 0 ≦ y ≦ 5, respectively).
And z is a number that satisfies x <z ≦ (x + 2)), and a basic substance is added to make the aqueous solution alkaline so that an R-containing salt or a Bi-containing salt as a hydroxide, A production method comprising a step of precipitating an Fe-containing salt and an M-containing salt and separating the precipitate from an aqueous solution. 6. The manufacturing method according to claim 5, wherein z is a number satisfying (1.1x) <z ≦ (x + 2). 7. The R-containing salt, Bi-containing salt, Fe-containing salt or M-containing salt wherein the base is a hydroxyl group.
The manufacturing method described in. 8. A bismuth rare earth iron garnet precursor composition according to claim 1, which is 400 to 700.
During is formula obtained by firing ° C. (1) [Formula 2] _{R 3-x Bi x Fe 5} -y M y O 12 (1) ( wherein, R is Y, La, Ce, Pr, Nd, Pm , S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, and one or more elements selected from the group consisting of Lu, M is Al, Ga, Cr, Mn, Sc, In, R
u, Rh, Co, Fe (II), Cu, Ni, Zn, L
i, Si, Ge, Zr, Ti, Hf, Sn, Pb, M
represents one or more elements selected from the group consisting of o, V and Nb, and R and Bi are c in the garnet crystal structure.
Occupies the sites, Fe and M occupy the a and / or d sites in the garnet crystal structure, and O occupies the h sites in the garnet crystal structure. x and y are 0 respectively
It is a number that satisfies <x ≦ 3 and 0 ≦ y ≦ 5. ) A magnetic ferrite powder mainly containing bismuth rare earth iron garnet.